Support custom android buildPatch with react-native link

[chrisbianca]

This PR: 5f14088 added support for more complex compile statements in build.gradle such as:

compile(project(':example') { … }

However, whilst react-native link can now detect the presence of such a compile statement, there is no way for a library developer to specify a compile statement of this format as part of their library linking. In our react-native-firebase library, we have such a requirement and need to be able to add the following:

    compile(project(':react-native-firebase')) {
        transitive = false
    }

This change adds an additional buildPatch option for the rnpm settings in a library's package.json file as follows:

  "rnpm": {
    "android": {
      "buildPatch": "    compile(project(':react-native-firebase')) {\n        transitive = false\n    }\n"
    }
  }

Test Plan

This commit adds additional test cases to makeBuildPatch.spec.js to validate that the buildPatch is correctly built in the instance where a buildPatch is supplied and to ensure backwards compatibility when it is not supplied.

I have also manually validated that the configuration works for react-native-firebase by applying the patch locally and running react-native link.

[facebook-github-bot]

@chrisbianca I tried to find reviewers for this pull request and wanted to ping them to take another look. However, based on the blame information for the files in this pull request I couldn't find any reviewers. This sometimes happens when the files in the pull request are new or don't exist on master anymore. Is this pull request still relevant? If yes could you please rebase? In case you know who has context on this code feel free to mention them in a comment (one person is fine). Thanks for reading and hope you will continue contributing to the project.